Schweitzer Engineering Laboratories SEL-734 - Energy Metering; Table 4.7 Example ANGCUT Setting

4.13
Date Code 20090730 Instruction Manual SEL-734 Meter
Metering
Energy Metering
To avoid influencing the demand metering peak recording for a system fault,
peak recording is momentarily suspended when Meter Word bit FAULT is
asserted (= logical 1). See the explanation for the FAULT setting in
Maximum/Minimum Metering on page 4.16.
Energy Metering
View or Reset Energy Metering Information
Via Serial Port
NOTE: Single-phase quantities are
available only in Form 9 models.
Use the MET E command to display accumulated single- and three-phase
megawatt-, megavoltamp-, and four-quadrant megavar-hours. The MET R E
command resets the accumulated single- and three-phase megawatt-,
megavoltamp-, and megavar-hours. Level 2AC access is required to reset
energy metering values.
Via Front Panel
The information and reset functions available via the previously discussed
serial port commands MET E and MET R E are also available via the
front-panel pushbuttons. See Figure 11.3.
Via Remote Bits and DNP
See Via Remote Bits and DNP on page 4.12.
Energy Metering
Updating and Storage
The SEL-734 updates energy values every second.
The meter saves energy values to nonvolatile memory once every minute (it
overwrites the previous stored value if it is exceeded). Should the meter lose
control power, it will restore the energy values saved by the meter during the
last save to nonvolatile memory. See Rollover on page 9.12 for the number of
digits displayed and rollover.
Energy Cut-Off Point As the power factor approaches zero, small phase angle measurement errors
result in relatively large errors in real power (watts) measurements. This is
because of the sensitivity of the cosine function as the phase angle approaches
90° (PF = 0).
To prevent erroneous real power measurements under near PF = 0 conditions,
the SEL-734 supports an energy cut-off angle using the ANGCUT (see SET G
Command on page SET.5) setting. When the phase angle between the current
and voltage reaches the cut-off setting, rms watts are zeroed. The ANGCUT
setting supports cut-off angles from 1° to 10°.
Reactive power (VAR) measurements are suppressed in a similar manner. See
Table 4.7.
Table 4.7 Example ANGCUT Setting
ANGCUT Setting Watts Zeroed Between VARs Zeroed Between
OFF n/a n/a
2 88° to 92° and –88° to –92° 2° to –2° and 178° to –178°
10 80° to 100° and –80° to –100° 10° to –10° and 170° to –170°
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